Explosion-proof enclosure for centrifuges and the like



C. J. FILZ Nov. 26, 1963 EXPLOSION-PROOF ENCLOSURE FOR CENTRIFUGES AND THE: LIKE EXPLOSION-PROOF ENcLosURE FOR CENTRIFUGES AND THE LIKE F11ed July 11, 1960 v C. J. FlLZ v Nov. 26, 1963 ATTORNEY United States Patent O 3,111,353 EXPLSEN-PRGF ENCLSURE FR CENYRELFUGES AND 1HE UKE Charles J. Filz, Weston, Cena., assigner to lvan Sori/all, luc., Norwalk, Conn., a corporation of New York Filed .luly 11, 196i), Ser. No. 41,952 6 Claims. (Q1. 74-69) This invent-ion relates to explosion-proof enclosures for centrifuges and the like, Iand more particularly to improved structural arrangements therefor.

In operating laboratory or industrial ccntrifuges, there is an ever present hazard, as a result of high `and ultra high speed rotation, that structural defects may cause the rotor to fracture whereby its fragments would be hurled about at ballistic speeds around the laboratory with serious personal and property damage as a consequence. Various protective enclosures have heretofore been utilized; in most cases, however, a compromise had to be made as to the wall thickness and weight since it was apparent that there were limitations in cost and size beyond which it was not feasible to go. Accordingly, previous enclosures, that were purportedly explosionproof, have not offered the best type of security that is desired in a laboratory.

Accordingly, the present invention concerns itself with providing an explosion-proof enclosure, wh-ich, while it is made of a strong steel container, is not necessarily so thick in its wall cross section that it is unwieldly or too costly; at the same time various structural arrangements are incorporated whereby the container walls fare prevented from being torn by the impact of parts hurled at projectile speed from a broken or exploded centrifuge rotor. The walls of the explosion-proof chamber of the present invention are arranged to yield under the impact of rotor fragments and to absorb their force under the release of shear bolts, while at the same time the complete collapse or fracture of said walls is prevented by novel interlocking and anchoring arrangements which ensure the integrity of the enclosure around a fracturing or exploding centrifuge rotor.

By this means the present invention obviates the necessity for surrounding the explosion-proof apparatus with a cabinet as a so-called second line of defense as has been necessary with heavy rigid apparatus of the prior art, where little or no yieldability was present in the wall structure.

Still other objects and advantages of the invention will be apparent from the specification.

The features of novelty which rare believed to be characteristic of the invention are set forth herein and Iwill best be understood, both as to their fundamental principles .and as to their particular embodiments, by reference to the speciication and `accompanying drawings, in which:

'FIGURE 1 is an enlarged section View, taken on line 1 1 of FIG. 2, some parts being broken away and some parts being shown in elevation and phantom outline;

FIG. 2 is a greatly reduced top view of the apparatus shown in FIG. l, some parts being broken away; and

FIG. 3 is a slightly reduced View taken on yline 3-3 of FIG. l, some parts being omitted, some parts being broken away.

Referring now to the drawings in detail, the explosionproof enclosure, generally, designated 11, comprises a unitary, vertically extending, circular, steel wall or housing 12 which defines `an explosion chamber 13 within which a centrifuge rotor 14 is concentnieally positioned. Rotor 14 may be generally of the size illustrated, or it may be the size indicated in the dashed outline 15, as shown in FIG. l. Rotor 14 is mounted on a drive shaft 16, the lower end of which is connected by suitable means 3,111,363 Patented Nov. 26, 1963 ICC to a motor, not shown. Shaft 16 is surrounded by a shaft housing 17 which is connected to a mounting ring 18 which forms the support for `a Imotor or the like.

An integral part of a structural base, cabinet, frame or the like, not shown, is the horizontal plate Z1 which has a central circular aperture bounded by an annular lip 22 which cooperates with `an annular recess 23 in ring 18, to form a secure connection therebetween. Attached to an outer portion of the top surface of base plate 21. by means of a plurality of shear pins or bolts 25 in circular array is a horizontal, steel anchor ring 26.

Base plate 21 has an upwardly extending ring-like boss 27 to the top horizontal surface of which is secured a circular steel retaining plate 2S by means of bolts 29. Both boss 27 and plate 28 have central apertures to provide clearance for mounting ring 18. Retaining plate 2S has 'a substantially larger diameter than boss 27 whereby the outer per-ipheral portions of said plate are spaced apart from the top surface of base plate 21. That peripheral portion of retaining plate 28 which extends over a circular portion of anchor ring 26 is spaced apart vertically fr-om the latter.

Connected to the top of retaining plate 28 by means of screws 31 is a ring 32 to the top of which is connected a stiff but somewhat resilient collar 33 made of rubber, neoprene, or the like, the inner portion of said collar being apertured and having a flexible, annular lip 34 which frictionally engages the peripheral surface of shaft housing 17 thereby sealing chamber 13 fnom deleterious materials or air currents that might otherwise enter said chamber.

The annular bottom edge of housing 12 is rigidly secured to the peripheral portion of anchor ring 26 by means of a strong welded annular joint 37. The inside diameter of housing 12 is somewhat greater than the peripheral diameter of retaining plate 28. Positioned between the periphery of retaining plate 2S and the inner wall of housing 12 and resting on the top surface of ring 2.6 is :a ring 33 made of a suitable resilient material, such as rubber, neoprene or the like, and in order to form an air and liquid seal, and to act as a sound absorbing mediurn.

The outer periphery of the upper portion of the wall of housing 12 has a horizontal annular recess 41 above which said wall is formed in an integral outwardly extending circular lip 42.

The open top of housing .12 4is enclosed by a circular convex steel cover d3 which may be provided at its apex with a central aperture 34. Cover 43` has a downwardly extending circular side wall 45 which terminates in an inwardly extending annular lip 46.

Hinge element 47 is firmly secured to cover wall 45 while hinge element 48 is rrnly secured to the side of housing 12, said two hinges being interconnected by pin 419 whereby cover 43 is mounted pivotally in respect of said housing. Cover t3 is secured in position on top of housing 12 by means of one or more suitable locking arnangements, each comprising, for example, a hook Si) connected by means of bracket 51 to the outer surface of housing 12 and which is engaged by a latching loop 52 connected to a pivoting latch 53 connected to bracket 54 mounted on cover wall d5. Latch 53 has an upwardly extending handle 55 which provides for manual operation of the latching device.

It will be noted from FIG. l that lip 46 of cover 43 rests upon the outer portion of the bottom of recess 41, and that the vertical dimension of lip 46 is somewhat smaller than the ve1tical dimension of recess 41. Also, the inner edge of lip 46 is spaced apart from the inner vertical Wall of recess 41.

ln the case of a fifteen pound centrifuge rotor running at 20,000 revolutions per rninute, for example, it would annees ordinarily be necessary to provide an explosion container whose steel walls and cover are in the order of ll/s" thick to provide for reasonable safety. Such a container is a fairly massive structure and would be unwieldy for use on the ordinary laboratory table. if the wall and cover were made somewhat thinner, it would then be necessary to provide an auxiliary cabinet around the chamber in order to provide la so-called second line of defense against the possible rupture of such thinner wall.

By employing the safety features embodied in the structural arrangement ofthe present invention, it is possible to 4reduce the wall thickness of the present explosion chamber to the order of 5/s", and the cover to the order of 1A thick.

ln the event of an accidental explosion or fracture of the rotor (i4 or l5) while the latter is rotating at high speed, fragments hurled therefrom at ballistic or projectile speeds and impinging upon the wall l2 of enclosure lll will cause said wall, or at least a portion thereof, to become distorted. `in the case of moderate impacts, wall l2 would retain its generally vertical position by virtue of bol-ts 25 holding `anchor plate 26 down on its plate 2li. In the event of :a drastic explosion, such as would take place when a rotor :fractures in two pieces, the impact upon `wall l2 would be so great as to cause the outward motion of wall l2 to the point where the force of the impact overcomes the predetermined shear resistance or limit of shear bolts Z5, whereby anchor pla-te 26 will be released or freed from base plate 2l. By tmeans of this releasing action of shear bolts 2.5, the outward movement of wall 25 provides a shock absorbing action for the impact of the fragments, whereby the accident is contained within chamber `ll. As a further insurance factor to contain the accident within the chamber, retainer plate 2E limits the pivotal motion of `anchor plate 2o and, accordingly, of wall l2. in order to prevent their complete dislocation from Ibase 2l.

A `further safety factor inherent in the structure illustrated and described herein is provided by the engagement or interlocking action between lip le of cover i3 and recess l of wall l2. Since the inner edge of lip 46 is initially spaced Iapart from fthe inner vertical surface of recess y(lll, it can be seen that wall l2 is permitted a certain amount of yieldable outward movement as a result of the rupture of shear fbolts 2S, which permits said wall to absorb the impact of fragments tlying from the fractured rotor. Such outward movement is limited or stopped when lip 46 becomes interlocked with recess 41. The interengagernent between lip 46 and recess 41 as a result of impacts upon wall l2 automatically locks cover 43 securely on the apparatus and serves to contain the ying fragments within the chamber. Since wall 12 has a modicu'm of ductility, the intermediate portion between the top and `bot-torn edges thereof may bulge outwardly under the impact of high speed fragments. This bulging action further helps to contain the explosion within the chamber -and keep the frag-ments ricochetting only into the interior of the chamber.

By virtue of the structures disclosed herein, there are multiple factors of safety incorporated -by simple means into the explosion chamber of the present invention which give assurance to the operators that accidents will be safely contained within the chamber. The wall 12 and cover 4-3 are made of a good quality of iductile steel, such as, for example, SAE 1020 or 1030, which will dis tort somewhat upon impact of fragments from an exploding rotor, but will not tear or fracture. Thus, there is incorporated into the steel wall itself a certain absorptive capacity for impacts, which further add-s to the safety features of the explosion chamber described herein.

IIt is claimed:

1. An explosion-proof enclosure for a centrifuge rotor or the like comprising `a horizontal base, a circular vertical wall connec-ted to said base and defining an enclosure for said rotor, Ia centrally located raised circular boss on said base within said enclosure, a horizont-al circular retainer Iplate mounted on said boss, a circular peripheral portion of said plate extending outwardly beyond the periphery of said boss, the portion of said plate extending beyond said boss being spaced apart from said base and forming a circular recess therewith, a horizontal anchor ring joined -securely to` the bottom of said wall, and a plurality of shear `bolts securing said anchor ring to said base, an inner circular portion of said anchor ring extending partially into said circular recess, the top surface of said rinrY inner portion being spaced apart from the bottom surface of said retainer plate portion.

2. An explosion-proof enclosure for a centrifuge rotor or the like comprising a base, a cylindrical vertical wall attached to said base and deiining an enclosure for said rotor, a retainer plate mounted on said base on the interior of said enclosure, the periphery of said plate being spaced apart from the inner surfaces of said wall, a circular portion of the bottom surface of said plate extending from the periphery thereof being spaced apart from the tcp surface oif'said base and forming an annular recess therewith, a ring connected to the bottom of said wall and extending inwardly into the interior of said enclf" re, an annular portion of said ring extending at least partially into said recess, the top surface of the portion of said ring extending into said recess being spaced apart from the bottom surface of said retainer plate, and a plurality of shear bolts securing said ring to said base.

3. An explosion-proof enclosure for a centrifuge rotor or the like comprising a bas a cylindrical vertical wall attached to said base and defining an enclosure for Said rotor, lirst means connected to said base in the interior of said enclosure, second means in the interior of said enclosure secured `firmly to the bottom of said wall, and third means releasably attaching sm'd second means to said base, said first means horizontally overlapping said second means and being spaced apart vertically therefrom, said tirst means limiting the upward movement of said second means when the latter is released by said third means.

4. An explosion-proof enclosure according to claim 3 and further comprising va horizontal annular recess in the outer surface of said wall and -at the upper end thereof, a cover mountable on top of said Wall, an inwardly extending anular lip at the bottom of said cover, the inner peripheral edge of Isaid lip being spaced part from the inner vertical Wall of said recess, said lip and said recess being dimensioned to interlock with each other when said vertical wall is moved outwardly under the impact of objects in the interior of said enclosure.

5. An explosion-proof enclosure according to claim 3 and further comprising la horizontal annular recess in the outer surface of said wall and at the upper end thereof, a cover mountable on top of said wall, an inwardly extending annular lip on said cover, said lip having a larger diameter than said recess whereby said lip and said recess are normally disengaged when said cover rests upon said wall, said lip and said recess becoming interlocked only when at least a portion of said wall is moved outwardly under the impact of objects in the interior of said enclosure.

6. An explosion-proof enclosure for a centrifuge or the like comprising a horizontal base, a circular vertical wall attached to said base and `delning an enclosure for said rotor, a horizontal circular retainer plate mounted on said base in the interior of said enclosure, a circular portion of the bottom surface of said plate extending from the periphery thereof bein-g spaced apart from the top surface of said base and forming an annular recess therewith, a ring connected to the bottom of said wall and extending inwardly into the interior of said enclosure, an annular portion of said ring extending at least partially l into said recess, a plurality of shear bolts securing said ring to said base, a horizontal annular recess in the outer surface of said Wall and at the upper end thereof, a cover mountable on top of said Wall, an inwardly extending annular lip at the bottom `of said cover, the inner 5 peripheral edge of said llip being spaced apart from the inner vertical wall of said recess, said lip and said recess interlocking with reach other only when at least a portion of said wall is moved outwardly under the impact 0f objects in the interior of said enclosure. 1

References Cited in the le of this patent UNITED STATES PATENTS Marzynski Mar. 26, Fleming et al. Dec. 23, Weinland May 19, Magnesen Jan. `18, Grela et al. Mar. 5, Melton Apr. 23, Pickels et al May 5, Rushing Aug. 16, 

3. AN EXPLOSION-PROOF ENCLOSURE FOR A CENTRIFUGE ROTOR OR THE LIKE COMPRISING A BASE, A CYLINDRICAL VERTICAL WALL ATTACHED TO SAID BASE AND DEFINING AN ENCLOSURE FOR SAID ROTOR, FIRST MEANS CONNECTED TO SAID BASE IN THE INTERIOR OF SAID ENCLOSURE, SECOND MEANS IN THE INTERIOR OF SAID ENCLOSURE SECURED FIRMLY TO THE BOTTOM OF SAID WALL, AND THIRD MEANS RELEASABLY ATTACHING SAID SECOND MEANS TO SAID BASE, SAID FIRST MEANS HORIZONTALLY OVERLAPPING SAID SECOND MEANS AND BEING SPACED APART VERTICALLY THEREFROM, SAID FIRST MEANS LIMITING THE UPWARD MOVEMENT OF SAID SECOND MEANS WHEN THE LATTER IS RELEASED BY SAID THIRD MEANS. 